Karts are motor vehicles that are used for leisure and sporting activities. In karts, a chain is often used to transmit power from the engine to the rear-wheel drive shaft; this chain is routed around an engine pinion and a sprocket that is mounted on the rear-wheel drive shaft.
Karts are often operated at high speeds, modern kart engines running at speeds of up to 21,000 rpm, which places extremely high stresses on the chain drive system. These can be linked to high rates of wear, a rapid loss of efficiency, short service life, and excessive noise. The outcome is that the chain, which is costly in and of itself, as well as the sprocket, have to be replaced at very short intervals.
FR 2302000 A proposes a drive system for karts where the chain drive has been replaced by a direct-drive/spur gearing system in order to eliminate the problems referred to above. The solution is not without its own disadvantages, including for example, the fact that complete encapsulation of the transmission, in order to prevent the egress of lubricating oil and the ingress of dirt, is difficult due to the separation of the engine from the transmission.
U.S. Pat. No. 7,000,727 B2 also proposes drive systems with a direct-drive/spur gearing system in order to eliminate at least some of the problems described above at least in part, in part by providing a housing to encapsulate the engine and transmission. Depending on the situation in which the kart is being used, a user of the kart may wish to have more torque (higher gear ratio), or alternatively may desire a higher top speed (lower gear ratio). Thus this solution has its own disadvantages, as the housing must still provide an opening in order to change the drive gear ratio of the spur gearing system. The arrangement of the gears substantially forward of the drive shaft and engine makes it difficult to change or replace gears while avoiding transmission oil leaking from the housing.
There is therefore a desire for a kart with a drive system which addresses the above described drawbacks.